Actuator bracket having a sensor

ABSTRACT

Actuator bracket having a sensor is disclosed. An example apparatus includes a bracket having a first side and a second side opposite the first side. The first side is to couple to a first surface of an actuator. The second side is to couple to a controller. The apparatus also includes a first sensor coupled to the first side of the bracket. When the bracket is coupled to the first surface of the actuator, the first sensor is adjacent the first surface to measure a characteristic of the first surface of the actuator.

FIELD OF THE DISCLOSURE

This patent relates generally to actuator brackets and, moreparticularly, to an actuator bracket having a sensor.

BACKGROUND

Actuators are commonly used to operate devices such as flow controlmembers in valves. A controller may be used to measure characteristicsof an actuator and control a position of a stem of the actuator. In someinstances, the controller is coupled to the actuator to enable thecontroller to control the actuator.

SUMMARY

In one example, an apparatus includes a bracket having a first side anda second side opposite the first side. The first side is to couple to afirst surface of an actuator. The second side is to couple to acontroller. The apparatus also includes a first sensor coupled to thefirst side of the bracket. When the bracket is coupled to the firstsurface of the actuator, the first sensor is adjacent the first surfaceto measure a characteristic of the first surface of the actuator.

In another example, an apparatus includes a bracket to couple acontroller to an actuator. The bracket has a first end, a second endopposite the first end, and a first side extending from the first end tothe second end. The first end is to couple to an actuator and the secondend is to couple to a controller. The apparatus also includes a firstsensor coupled to the first side at the first end of the bracket. Thefirst sensor is to measure a characteristic of the first end when thebracket is coupled to the actuator.

In another example, an apparatus includes means for coupling acontroller to a surface of an actuator and means for sensing acharacteristic coupled to the means for coupling. When the means forcoupling is coupled to the actuator, the means for sensing is adjacentthe surface to measure a characteristic of the means for coupling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example bracket assembly for coupling a controller toan actuator in accordance with the teachings herein.

FIG. 2 depicts a first side of a bracket of the bracket assembly of FIG.1.

FIG. 3 depicts a second side of the bracket of FIG. 2.

FIG. 4 depicts the example bracket assembly of FIG. 1 having the bracketof FIGS. 2-3 and a sensor.

FIG. 5 depicts the example bracket assembly of FIG. 1 having the bracketof FIGS. 2-3 and two sensors.

FIG. 6 depicts the example bracket assembly of FIG. 1 having a sensorcoupled to the actuator.

FIGS. 7A-7C depict example acceleration measurements of the examplebracket assembly of FIG. 1.

FIG. 8 depicts acceleration spectral densities associated with theacceleration measurements of FIGS. 7A-7C.

FIG. 9 depicts cumulative acceleration spectra associated with theacceleration spectral densities of FIG. 8.

The figures are not to scale. Instead, to clarify multiple layers andregions, the thicknesses of the layers may be enlarged in the drawings.Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like parts.

DETAILED DESCRIPTION

Controllers may be used to control actuators that operate valves. Forexample, some known controllers may be used to control a position of anactuator stem that is operatively coupled to a flow control member of avalve by providing control fluid to the actuator. To enable thecontroller to accurately provide the control fluid to the actuator, someknown controllers are coupled to a yoke of the actuator via a bracket.In some instances, repeated movement and/or vibration of the actuatormay loosen the bracket from the actuator and/or the controller overtime. A loose coupling between the bracket and the actuator and/orbetween the bracket and the controller may result in imprecise controlof the actuator and/or structural damage to the actuator, the bracketand/or the controller. For example, if the bracket remains looselycoupled to the actuator for an extended period of time, continuedvibration and/or movement of the actuator may result in the bracket andthe controller decoupling from the actuator. Additionally oralternatively, repeated movement and/or vibration of the actuator maydamage other components of the actuator. In some examples, vibrations ofthe actuator may cause cracking of the yoke, loosening of a yoke locknut and/or failure of supply line tubing between the controller and theactuator.

The example bracket disclosed herein includes a sensor to measure acharacteristic of an actuator and/or a bracket coupling a controller tothe actuator. For example, the sensor measures a characteristic of thebracket or the actuator that is indicative of a degree to which thebracket is securely and/or rigidly coupled to the actuator. Toaccurately measure the characteristic of the coupling, the sensor ispositioned immediately adjacent to where the bracket couples to theactuator. Further, the characteristic measured by the sensor isindicative of a characteristic of an actuator yoke, a yoke lock nut,actuator supply line tubing and/or a coupling of the bracket and acontroller. In some examples, the bracket includes a second sensor. Acomparison of characteristics measured by the sensors further enablesidentification of a characteristic of the actuator yoke, the yoke locknut, the actuator supply line tubing, the coupling of the bracket andthe controller and/or the coupling of the bracket and the actuator.Thus, the example bracket monitors the bracket and/or the actuator todetect failure and/or degradation of the actuator, the bracket, thecoupling between the bracket and the actuator and/or the couplingbetween the controller and the actuator.

An example bracket assembly disclosed herein includes a bracket having afirst side that is to couple to a first surface of an actuator and asecond side that is to couple to a controller. A first sensor (e.g., aforce gauge, a strain gauge, an accelerometer, an acoustic emissionsensor) of the example bracket assembly is coupled to the first side ofthe bracket. When the bracket of the example bracket assembly is coupledto the first surface of the actuator, the first sensor is adjacent thefirst surface to measure a characteristic (e.g., stress, strain,acceleration of vibrations, acoustic emissions) of a coupling of theactuator. For example, by measuring acceleration of vibrations of aportion of the bracket that is adjacent the coupling, the first sensoridentifies if the bracket is loosened and/or decoupled from theactuator.

In some examples, the first sensor of the example bracket assembly iscoupled to the bracket between ribs defined by the first side of thebracket and recessed from an outer edge of the ribs to protect the firstsensor from being damaged. At least one of the ribs has an outer edgethat defines a groove to receive a wire coupled to the first sensor. Thegroove prevents the wire from being pinched, severed and/or otherwisedamaged when the bracket is coupled to the actuator. Thus, the examplebracket apparatus substantially reduces the risk of the sensor beingdamaged or dislodged.

In some examples, the bracket has a first end that is to couple to theactuator and a second end opposite the first end that is to couple tothe controller. The first sensor is coupled at the first end of thebracket and a second sensor is coupled at the second end of the bracket.The second sensor measures a characteristic of the second end when thecontroller is coupled to the bracket. In such examples, thecharacteristics measured by the first sensor and the second sensor arecompared to determine if the controller is loosened and/or decoupledfrom the bracket.

In some examples, the bracket assembly includes another sensor that isto couple to a second surface of the actuator different than the firstsurface. The other sensor measures a characteristic of the secondsurface of the actuator. In some examples, the first sensor and theother sensor are communicatively coupled to the controller to enable thecharacteristic of the coupling and the second surface of the actuator tobe compared. For example, by comparing the characteristics of thecoupling and the second surface of the actuator, the controller candetermine if an actuator component adjacent the second surface of theactuator (e.g., a component of an actuator casing, a diaphragm plate) isloosened and/or decoupled.

FIG. 1 illustrates an example bracket assembly 100 in accordance withthe teachings herein. An actuator 102 of the illustrated examplecontrols fluid flow through a fluid valve 104. For example, the actuator102 includes a yoke 106, a yoke lock nut 107, a stem 108, tubing 110,and an actuator casing 112. The yoke 106 couples the actuator casing 112and the fluid valve 104. The tubing 110 operatively couples a controller114 (e.g., a positioner) to a pressure chamber defined by the actuatorcasing 112. The stem 108 operatively couples a diaphragm within thepressure chamber and a valve plug of the fluid valve 104.

In operation, the controller 114 measures a current position of the stem108. Based on the current position and a desired position of the stem108, the controller 114 provides control fluid (e.g., pressurized air)to the pressure chamber via the tubing 110 to change a pressure withinthe pressure chamber. The change in pressure causes the diaphragm and,thus, the stem 108 of the actuator 102 to move. In turn, the stem 108causes the valve plug to move relative to a valve seat of the fluidvalve 104 to increase and/or decrease fluid flow through the fluid valve104. Thus, the controller 114 of the illustrated example controls thefluid flow through the fluid valve 104.

In the illustrated example, the controller 114 is coupled to the yoke106 to enable the controller 114 to precisely control the actuator 102.For example, coupling the controller 114 to the actuator 102 enables thecontroller 114 to accurately measure the position of the stem 108 and/orreduce the distance that the control fluid travels between thecontroller 114 and the pressure chamber. As illustrated in FIG. 1, thecontroller 114 is coupled to the actuator 102 via a bracket 116 of theexample bracket assembly 100. A first end 118 of the bracket 116 iscoupled to the yoke 106 via fasteners 120 to form a coupling 122 of thebracket 116 and the actuator 102. The controller 114 of the illustratedexample couples to a second end (e.g., a second end 202 of FIG. 2) ofthe bracket 116 opposite the first end 118. In some examples, the secondend 202 of the bracket 116 is unsupported by or free from the actuator102. In other words, the bracket assembly 100 forms a cantilever inwhich the first end 118 is fixed to the yoke 106 and the second end 202is an unsupported end.

FIG. 2 depicts a first side 204 of the bracket 116. As illustrated inFIG. 2, the bracket 116 includes the first end 118 and the second end202 opposite the first end 118. The first end 118 of the bracket 116defines apertures 206, and the second end 202 of the bracket 116 definesapertures 208. The apertures 206, 208 of the bracket 116 extend betweenthe first side 204 and an opposing second side (e.g., a second side 302of FIG. 3) of the bracket 116.

In the illustrated example, the first side 204 at the first end 118 ofthe bracket 116 is to couple to a surface of the yoke 106 (FIG. 1) tosecurely fix, couple and/or fasten the bracket 116 to the actuator 102(FIG. 1). To couple the bracket 116 to the actuator 102, the apertures206 at the first end 118 of the illustrated example are to align withrespective apertures or bores of the yoke 106. The fasteners 120(FIG. 1) are to extend through the respective apertures 206 of thebracket 116 and be received by the apertures or bores of the yoke 106.In some examples, the fasteners 120 are threaded and received byrespective threaded apertures or bores of the yoke 106. To ensure thatthe bracket 116 is rigidly fixed, coupled and/or fastened to theactuator 102, the threaded fasteners 120 are rotated until the coupling122 (FIG. 1) of the bracket 116 and the actuator 102 is secure.

As illustrated in FIG. 2, the first side 204 of the bracket 116 definesribs 210 to increase a rigidity of the bracket 116. In the illustratedexample, an outer edge 212 of each of the ribs 210 forms an outersurface 214 of the first side 204 of the bracket 116. A recessed surface216 of the first side 204 is spaced apart from the outer surface 214 ina direction toward the second side 302. As illustrated in FIG. 2, theribs 210 intersect to form a web-like pattern such that the ribs 210 andthe recessed surface 216 define cavities 218. In some example, the ribs210 form polygonal profiles of the respective cavities 218. For example,some of the cavities 218 of FIG. 2 have triangular shapes or profiles.

The bracket assembly 100 of the illustrated example includes a sensor220 that is coupled to the first side 204 of the bracket 116. Asillustrated in FIG. 2, the sensor 220 is fixed to the recessed surface216 within a cavity 222 (e.g., one of the cavities 218) adjacent thefirst end 118 of the bracket 116. The sensor 220 is coupled to therecessed surface 216 via, for example, an adhesive, potting materialand/or a mechanical fastener. In the illustrated example, the sensor 220is disposed within the cavity 222 to protect the sensor 220 from beingdamaged and/or dislodged by other objects (e.g., the actuator 102). Thesensor 220 is fixed between the apertures 206 to enable the sensor 220to measure a characteristic of the coupling 122 of the bracket 116 andthe actuator 102.

As illustrated in FIG. 2, the sensor 220 is coupled to a first end 224of a cable or wire 226 that communicatively couples the sensor 220 andthe controller 114 (FIG. 1). The wire 226 enables the sensor 220 tocommunicate the measured characteristics of the first end 118 of thebracket 116 to the controller 114. In some examples, the wire 226includes an electrically-insulating coating or jacket to prevent thewire 226 from shorting to the bracket 116 and/or any other object. Inthe illustrated example, a second end 228 of the wire 226 opposite thefirst end 224 extends through an opening 230 defined by the bracket 116.The opening 230 enables the second end 228 of the wire 226 to couple tothe controller 114. As illustrated in FIG. 2, the opening 230 extendsbetween the recessed surface 216 of the first side 204 and the secondside 302 of the bracket 116.

In the illustrated example, at least one of the ribs 210 defined by thefirst side 204 is positioned between the sensor 220 and the opening 230.As illustrated in FIG. 2, each of the ribs 210 positioned between thesensor 220 and the opening 230 define a groove 232 that receives thewire 226. For example, the wire 226 is fixedly received by the grooves232 via potting material, an adhesive and/or a mechanical fastener. Inother examples, the ribs 210 define apertures spaced apart from theouter edge 212 of the ribs 210 through which the wire 226 extends fromthe sensor 220 to the opening.

In some examples, the grooves 232 enable the wire 226 to be recessedfrom the outer edge 212 of the ribs 210. As a result, the grooves 232substantially reduce the risk of the wire 226 being damaged by theactuator 102 and/or any other object. For example, the grooves 232prevent the wire 226 from being pinched, severed and/or otherwisedamaged by the actuator 102 when the bracket 116 is coupled to theactuator 102.

FIG. 3 depicts the second side 302 of the bracket 116 that is oppositethe first side 204 shown in FIG. 2. The apertures 208 defined at thesecond end 202 of the illustrated example enable the controller 114(FIG. 1) to couple to the second side 302 at the second end 202 of thebracket 116. The apertures 208 at the second end 202 are to align withrespective apertures or bores of the controller 114. To securely and/orrigidly couple the controller 114 to the bracket 116, fasteners (e.g.,fasteners 402 of FIG. 4) extend through the respective apertures 208 ofthe bracket 116 and are received by the respective apertures or bores ofthe controller 114. In some examples, the fasteners 402 are threaded andare received by respective threaded apertures or bores of the controller114.

FIG. 4 depicts the example bracket assembly 100 coupled to thecontroller 114. In the illustrated example, the controller 114 iscoupled to the second side 302 of the bracket 116 via the fasteners 402(e.g., threaded fasteners) that extend through the apertures 208 (FIG.2) of the bracket 116. Thus, as illustrated in FIG. 4, the controller114 is coupled to the second side 302 at the second end 202 of thebracket 116.

In the illustrated example, the sensor 220 is coupled to first side 204at the first end 118 of the bracket 116 and is communicatively coupledto the controller 114 via the wire 226. The first end 224 of the wire226 is coupled to the sensor 220, and the second end 228 of the wire 226is coupled to the controller 114 via a terminal or receptacle 404 of thecontroller 114. As illustrated in FIG. 4, the second end 228 of the wire226 extends through the opening 230 of the bracket 116 and is receivedby the receptacle 404 adjacent the opening 230. In some examples, theopening 230 is defined by the bracket 116 such that the opening 230aligns with the receptacle 404 when the controller 114 is coupled to thebracket 116.

As illustrated in FIG. 4, the sensor 220 is disposed in the cavity 222between the apertures 206 that enable the bracket 116 to couple to theactuator 102 (FIG. 1). When the bracket 116 of the illustrated exampleis coupled to a surface of the actuator 102, the sensor 220 is enclosedby the recessed surface 216, the adjacent ribs 210, and the surface ofthe actuator 102. As a result, the sensor 220 is protected from beingdislodged and/or damaged by the actuator 102 and/or any other objectwhen the bracket 116 is coupled to the actuator 102.

The sensor 220 of the illustrated example measures a characteristic of aportion 406 of the bracket 116 immediately adjacent the coupling 122(FIG. 1) of the bracket 116 and the actuator 102. Because the portion406 is immediately adjacent the coupling 122, the characteristics of theportion 406 measured by the sensor 220 are substantially similar (e.g.,identical) to the characteristics of the coupling 122. As a result, thesensor 220 is able to accurately measure a characteristic of thecoupling 122 when the sensor 220 is coupled to the first end 118 of thebracket 116. Thus, the sensor 220 is capable of accurately measuring acharacteristic (e.g., a force, a strain, an acceleration, an acousticemission) that indicates whether the coupling 122 of the bracket 116 andthe actuator 102 is secure and/or rigid. Otherwise, if the sensor 220 issubstantially spaced apart from the coupling 122, the measurements ofthe sensor 220 may not accurately reflect a characteristic of thecoupling 122. In some example, the characteristic measured by the sensor220 is further indicative of whether the yoke 106 of the actuator 102 iscracked, the yoke lock nut 107 is loosened, the tubing 110 has failedand/or the controller 114 is securely coupled to the bracket 116.

The sensor 220 of the illustrated example is an accelerometer. In someexamples, the sensor 220 is a single-axis accelerometer or a tri-axialaccelerometer. A single-axis accelerometer measures a properacceleration (e.g., g-force) of an object (e.g., the first end 118 ofthe bracket 116) in one direction, and a tri-axial accelerometermeasures a proper acceleration of an object in three perpendiculardirections. For example, accelerometers are used to measureaccelerations of vibrations of machinery (e.g., the actuator 102). Themeasured accelerations of vibrations are used to calculate anacceleration spectral density to detect degradation and/or failureinitiation of the rotary machinery. Acceleration spectral density is acalculation of the square of the average amplitude of a vibration at avibration frequency bandwidth (e.g., square of the root mean squareg-level of a signal over a frequency bandwidth (grms²/Hz)).

In the illustrated example, the acceleration spectral density iscalculated based on the accelerations of vibrations measured by thesensor 220 of the portion 406 at the first end 118 of the bracket 116.Because the portion 406 is immediately adjacent the coupling 122, thecontroller 114 analyzes the calculated acceleration spectral density(e.g., via Fourier transform analysis, Cepstrum analysis, skewness andkurtosis analysis, phase and modal analysis, etc.) to determine whetherthe bracket 116 is securely and/or rigidly fixed, fastened and/orcoupled to the actuator 102. For example, when the fasteners 120(FIG. 1) that couple the first end 118 of the bracket 116 to the yoke106 (FIG. 1) are loose, the controller 114 identifies a shift in aresonant frequency (e.g., a positive or negative shift) and/or a changein a frequency amplitude (e.g., a dampening or amplification) of thecalculated acceleration spectral density that is indicative of a loosecoupling. In some examples, a shift in a resonant frequency and/or achange in a frequency amplitude of the calculated acceleration spectraldensity is indicative of the yoke 106 cracking, the yoke lock nut 107loosening, the tubing 110 failing and/or the controller 114 decouplingfrom the bracket 116.

While the sensor 220 of the illustrated example is an accelerometer,other types of sensors may be used to identify a characteristic of thebracket 116 and/or the actuator 102. In some examples, the sensor 220 isa force gauge that measures a force imparted to the portion 406 of thebracket 116. In some examples, the sensor 220 is a strain gauge thatmeasures a strain of the portion 406 of the bracket 116. In someexamples, the sensor 220 is an acoustic emission sensor that measuresacoustic emissions of the first end 118 of the bracket 116 to determineif the bracket 116 and/or the actuator 102 are physically altered. Forexample, the acoustic emission sensor can identify whether the bracket116 has been physically altered in such a manner that compromises thecoupling 122 of the bracket 116 and the actuator 102 (e.g., a crack hasformed along one of the apertures 206).

FIG. 5 depicts the example bracket assembly 100 that includes the sensor220 coupled to the first end 118 of the bracket 116 and a sensor 502coupled to the second end 202. As illustrated in FIG. 5, the controller114 is coupled to the second side 302 at the second end 202 of thebracket 116 via the fasteners 402, and the sensor 220 is coupled to thefirst side 204 at the first end 118 of the bracket 116. The wire 226 iscoupled to the sensor 220 and is received by the receptacle 404 of thecontroller 114 to communicatively couple the sensor 220 and thecontroller 114.

In the illustrated example, the sensor 502 is coupled to the recessedsurface 216 of the first side 204 at the second end 202 of the bracket116. The sensor 502 is disposed within a cavity 504 (e.g., one of thecavities 218) at the second end 202 of the bracket 116 to protect thesensor 502 from being damaged and/or dislodged. The sensor 502 iscoupled to the bracket 116 via, for example, an adhesive, pottingmaterial and/or a mechanical fastener.

As illustrated in FIG. 5, the sensor 502 is communicatively coupled tothe controller 114 via a cable or wire 506. A first end 508 of the wire506 is coupled to the sensor 502. A second end 510 of the wire 506opposite the first end 508 extends through the opening 230 of thebracket 116 and is received by a receptacle 512 of the controller 114.As illustrated in FIG. 5, each of the ribs 210 positioned between thesensor 502 and the opening 230 defines one of the grooves 232 thatsubstantially reduce the risk of the wire 506 being pinched, severedand/or otherwise damaged.

To enable the measurement of the sensor 502 to be compared to themeasurement of the sensor 220, each of the sensors 220, 502 of theillustrated example of FIG. 5 is an accelerometer. For example, thesensor 220 measures the acceleration at the first end 118 of the bracket116, and the sensor 502 measures the acceleration at the opposing secondend 202. Based on the measured accelerations, the controller 114calculates an acceleration spectral density associated with the bracket116. In other examples, both of the sensors 220, 502 are a force gauge,a strain gauge, an acoustic emission sensor, or another type of sensorthat enable the measurement of the sensor 502 to be compared to themeasurement of the sensor 220.

Because the bracket 116 of illustrated example is coupled to theactuator 102 only at the first end 118, the second end 202 of thebracket 116 is unsupported. As a result, vibrational energy of thebracket 116 is transmitted across the bracket 116 (e.g., from the firstend 118 to the second end 202). In some examples, the accelerationspectral density calculated from the acceleration measurements of thesensors 220, 502 indicates a vibrational energy characteristic of thebracket 116. For example, the controller 114 analyzes the accelerationspectral density (e.g., via e.g., via Fourier transform analysis,Cepstrum analysis, skewness and kurtosis analysis, phase and modalanalysis, etc.) to calculate or determine a transmissibility of thebracket 116 that represents a ratio of vibrational energy transmittedthrough the bracket 116. Thus, to determine the transmissibility of thebracket 116, measurements of the sensor 502, 220 are compared when thecontroller 114 is securely coupled to the second end 202 and the firstend 118 is securely coupled to the actuator 102.

As illustrated in FIG. 5, the sensor 502 is coupled to the bracket 116between the apertures 208 to enable the sensor 502 to measure acharacteristic of a portion 514 of the second end 202 of the bracket116. Because the portion 514 of the bracket 116 is immediately adjacenta coupling 516 of the bracket 116 and the controller 114, thecharacteristics of the portion 514 are substantially similar (e.g.,identical) to the characteristics of the coupling 516. Further, thefirst sensor 220 measures a characteristic of the portion 406 of thefirst end 118 of the bracket 116. In some examples, a comparison of themeasured characteristics of the sensors 220, 502 identifies degradationand/or damage of the actuator 102, the bracket 116, the coupling 122 ofthe bracket 116 and the actuator 102 and/or the coupling 516 of thecontroller 114 and the bracket 116.

For example, the sensors 220, 502 of the illustrated example enable thecontroller 114 to determine whether the controller 114 is securelyand/or rigidly fixed, fastened and/or coupled to the second end 202 ofthe bracket 116. If a comparison of the measurements of the sensors 220,502 corresponds to the transmissibility of the bracket 116, thecontroller 114 determines that the controller 114 is securely and/orrigidly coupled to the bracket 116. Conversely, the controller 114determines that the controller 114 is unsecure and/or loosely coupled tothe bracket 116 if a comparison of the measurements of the sensors 220,502 identifies a shift in the resonant frequency and/or a change in thefrequency amplitude that is indicative of a loose coupling. Thus, thesensors 220, 502 of the bracket assembly 100 enable the controller todetermine whether the controller 114 is rigidly coupled to the bracket116.

In some examples, a shift in the resonant frequency and/or a change inthe frequency amplitude identified by a comparison of the measuredcharacteristics of the sensors 220, 502 is further indicative of theyoke 106 cracking, the yoke lock nut 107 loosening, the tubing 110failing and/or the coupling 122 between the bracket 116 and the actuator102 loosening. For example, a shift in the resonant frequency and/or achange in the frequency amplitude by a first predetermined value isindicative of the coupling 516 of the controller 114 and the bracket 116loosening, and a shift in the resonant frequency and/or a change in thefrequency amplitude by a second predetermined value different than thefirst predetermined value is indicative of the yoke 106 cracking.

FIG. 6 depicts the example bracket assembly 100 coupled to the yoke 106of the actuator 102. In the illustrated example, the bracket assembly100 includes the bracket 116, the sensor 220 (FIG. 2) coupled to thefirst end 118 of the bracket 116, and a sensor 602 coupled to theactuator 102. In the illustrated example, the sensor 602 is coupled to asurface 604 of a lower portion 606 of the actuator casing 112. A wire608 is coupled between the sensor 602 and the controller 114 (e.g., viathe receptacle 512 of FIG. 5) to communicatively couple the sensor 602and the controller 114.

Each of the sensors 220, 602 of the illustrated example is anaccelerometer that is communicatively coupled to the controller 114. Asa result, the controller 114 is able to calculate an accelerationspectral density by comparing the acceleration measured at the surface604 of the actuator casing 112 and the acceleration measured at thecoupling 122 of the bracket 116 and the yoke 106. In other examples,both of the sensors 220, 602 are a force gauge, a strain gauge, anacoustic emission sensor, or another type of sensor to enable themeasurements of the sensors 220, 602 to be compared by the controller114.

In the illustrated example, the sensors 220, 602 enable the controller114 to determine if a component of the actuator casing 112 (e.g., thelower portion 606 or an opposing upper portion 610 of the actuatorcasing 112) and/or another component (e.g., a diaphragm disposed withina cavity of the actuator casing 112) near the surface 604 of theactuator casing 112 is unsecure and/or loosely fixed. For example, ameasurement of the sensor 220 is compared to a measurement of the sensor602. The sensors 220, 602 identify degradation and/or decoupling of acomponent of the actuator casing 112 if there is a shift in a resonantfrequency (e.g., a positive or negative shift) and/or a change in afrequency amplitude (e.g., a dampening or amplification) away frommeasurements of the sensors 220, 602 that are indicative of the actuatorcasing 112 being undamaged. In some examples, the calculatedacceleration spectral density indicates a shift in the resonantfrequency and/or a change in the frequency amplitude by a predeterminedvalue that is associated with a loosening of bolts 612 that couple thelower and upper portions 606, 610 of the actuator casing 112. In suchexamples, the controller 114 communicatively coupled to the sensors 220,602 determines that the bolts 612 have loosened from the lower portion606 and/or the upper portion 610 of the actuator casing 112. Thus, thesensors 220, 602 of the bracket assembly 100 enable the controller 114to determine whether components of the actuator 102 are securelyfastened.

FIGS. 7A-7C depict example acceleration measurements of the bracketassembly 100 of FIG. 1. FIG. 7A depicts acceleration measurements 702with a solid line, FIG. 7B depicts acceleration measurements 704 with adashed line, and FIG. 7C depicts acceleration measurements 706 with adotted line. In the illustrated examples, the acceleration measurements702, 704, 706 are represented by g-force (G) of the acceleration over aperiod of time (e.g., 2 seconds). In some examples, the accelerationmeasurements 702, 704, 706 are obtained from the sensor 220 (FIG. 2)that is positioned at the first end 118 of the bracket 116 and thesensor 502 (FIG. 5) that is positioned at the second end 202 of thebracket 116.

In the illustrated examples, the acceleration measurements 702 of FIG.7A are associated with a first period of time, the accelerationmeasurements 704 of FIG. 7B are associated with a subsequent secondperiod of time, and the acceleration measurements 706 of FIG. 7C areassociated with a subsequent third period of time. For example, theacceleration measurements 702 of FIG. 7A are obtained during a firstday, the acceleration measurements 704 of FIG. 7B are obtained during asubsequent second day, and the acceleration measurements 706 of FIG. 7Care obtained during a subsequent third day.

FIG. 8 depicts acceleration spectral densities 802, 804, 806 that arecalculated based on the respective acceleration measurements 702, 704,706 of FIGS. 7A-7C. The acceleration spectral densities 802, 804, 806 ofthe bracket 116 are shown over a range of frequencies (e.g., 0-40 Hz) inFIG. 8. In the illustrated example, the acceleration spectral density802 associated with the first time period is represented with a solidline, the acceleration spectral density 804 associated with the secondtime period is represented with a dashed line, and the accelerationspectral density 806 associated with the third time period isrepresented with a dotted line.

As illustrated in FIG. 8, the acceleration spectral densities 802, 804,806 indicate respective resonant frequencies 808, 810, 812 of thebracket 116. The resonant frequency 808 is associated with the firstperiod of time, the resonant frequency 810 is associated with the secondperiod of time, and the resonant frequency 812 is associated with thethird period of time.

In the illustrated example, the resonant frequencies 808, 810, 812 ofthe bracket 116 indicate that the structural rigidity of the bracket 116decreases (e.g., cracking growth of the bracket 116, loosening of thecoupling 122 between the bracket 116 and the actuator 102, etc.) fromthe first period of time to the third period of time. In the illustratedexample, the decrease in structural rigidity is identified by a negativeshift of the resonant frequencies 808, 810, 812 over time. For example,a resonant frequency of the bracket 116 decreases from 30 Hz during thefirst period of time (e.g., the resonant frequency 808) to 28.5 Hzduring the second period of time (e.g., the resonant frequency 810) to22.5 Hz during the third period of time (e.g., the resonant frequency812). Further, the resonant frequencies 808, 810, 812 of the illustratedexample include additional and/or alternative indications of a decreasein structural rigidity. For example, the decrease in amplitudes of therespective resonant frequencies 808, 810, 812 over time and the increasein kurtosis of the respective resonant frequencies 808, 810, 812 (e.g.,represented by a widening of the peaks of the resonant frequencies 808,810, 812) represent an increase in vibrational energy over time and,thus, indicate a decrease in structural rigidity of the bracket 116 overtime.

FIG. 9 depicts cumulative acceleration spectra 902, 904, 906 associatedwith the acceleration spectral densities 802, 804, 806 of FIG. 8. Thecumulative acceleration spectra 902, 904, 906 are shown in FIG. 9 over arange of frequencies (e.g., 0-40 Hz) until each of the cumulativeacceleration spectra 902, 904, 906 is substantially equal to a value of1.0. In the illustrated example, the cumulative acceleration spectrum902 associated with the first time period is represented with a solidline, the acceleration spectral density 904 associated with the secondtime period is represented with a dashed line, and the accelerationspectral density 906 associated with the third time period isrepresented with a dotted line. In the illustrated example, a curve thatreaches a cumulative acceleration spectrum of 1.0 at a lower frequencyindicates decreased structural rigidity (e.g., as a result of crackgrowth, decoupling, etc.). Thus, the cumulative acceleration spectra902, 904, 906 indicate that the structural rigidity of the bracket 116decreases between the first period of time and the third period of time.

Although certain example apparatus have been described herein, the scopeof coverage of this patent is not limited thereto. On the contrary, thispatent covers all methods, apparatus and articles of manufacture fairlyfalling within the scope of the amended claims either literally or underdoctrine of equivalents.

What is claimed is:
 1. An apparatus comprising: a bracket having a firstside and a second side opposite the first side, the first side to coupleto a first surface of an actuator, the second side to couple to acontroller; and a first sensor coupled to the first side of the bracket,wherein, when the bracket is coupled to the first surface of theactuator, the first sensor is adjacent the first surface to measure acharacteristic of the first surface of the actuator.
 2. The apparatus ofclaim 1, wherein the characteristic of the first surface of the actuatorindicates a characteristic of at least one of a coupling of the bracketand the actuator, a coupling of a controller and the bracket, a yoke ofthe actuator, a yoke lock nut, and tubing between the controller and theactuator.
 3. The apparatus of claim 1, wherein the first side of thebracket defines ribs to increase a rigidity of the bracket.
 4. Theapparatus of claim 3, wherein the first sensor is coupled to the bracketbetween at least two of the ribs and is recessed from an outer edge ofthe ribs to enclose the first sensor by the at least two of the ribs,the first side of the bracket, and the first surface of the actuator. 5.The apparatus of claim 3, wherein an outer edge of at least one of theribs defines a groove to fixedly receive a wire coupled to the firstsensor via potting, the groove to prevent the wire from being damagedwhen the bracket is coupled to actuator.
 6. The apparatus of claim 1,wherein the bracket defines an aperture that is to receive a wireextending between the first sensor and a receptacle of the controller tooperatively couple the first sensor and the controller.
 7. The apparatusof claim 1, wherein the first sensor is an accelerometer, an acousticemission sensor, a force gauge, or a strain gauge.
 8. The apparatus ofclaim 1, further comprising a second sensor coupled to the first side ofthe bracket and spaced apart from the first sensor, wherein acharacteristic measured by the second sensor and the characteristicmeasured by the first sensor are compared to identify a characteristicof at least one of a coupling of the bracket and the actuator, acoupling of a controller and the bracket, a yoke of the actuator, a yokelock nut, and tubing between the controller and the actuator.
 9. Theapparatus of claim 1, further comprising a second sensor that is tocouple to a second surface of the actuator different than the firstsurface, the second sensor to measure a characteristic of the secondsurface of the actuator.
 10. The apparatus of claim 9, wherein, when thebracket is coupled to the controller and the actuator, the first sensorand the second sensor are operatively coupled to the controller toenable the characteristic of the coupling to be compared to thecharacteristic of the second surface.
 11. An apparatus comprising: abracket to couple a controller to an actuator, the bracket having afirst end, a second end opposite the first end, and a first sideextending from the first end to the second end, wherein the first end isto couple to an actuator and the second end is to couple to acontroller; and a first sensor coupled to the first side at the firstend of the bracket, the first sensor to measure a characteristic of thefirst end when the bracket is coupled to the actuator.
 12. The apparatusof claim 11, wherein the characteristic of the first end identifies acharacteristic of at least one of a coupling of the bracket and theactuator, a coupling of the controller and the bracket, a yoke of theactuator, a yoke lock nut, and tubing between the controller and theactuator.
 13. The apparatus of claim 11, wherein the first end of thebracket defines apertures extending between the first side and a secondside opposite the first side, the apertures to receive fasteners tocouple the first end of the bracket to the actuator.
 14. The apparatusof claim 13, wherein the first sensor is coupled to the first side ofthe bracket adjacent the apertures.
 15. The apparatus of claim 11,wherein the second end of the bracket defines apertures extending fromthe first side to a second side opposite the first side, the aperturesto receive fasteners to couple the second side at the second end of thebracket to the controller.
 16. The apparatus of claim 11, furthercomprising a second sensor coupled to the first side at the second endof the bracket, the second sensor to measure a characteristic of thesecond end when the bracket is coupled to the actuator.
 17. Theapparatus of claim 16, wherein a comparison of the characteristic of thefirst end and the characteristic of the second end identify acharacteristic of at least one of a coupling of the bracket and theactuator, a coupling of the controller and the bracket, a yoke of theactuator, a yoke lock nut, and tubing between the controller and theactuator.
 18. The apparatus of claim 16, wherein each of thecharacteristics is an acceleration used to calculate an accelerationspectral density associated with the bracket, the acceleration spectraldensity enables a transmissibility of the bracket to be calculated todetermine a characteristic of at least one of the bracket and theactuator.
 19. An apparatus comprising: means for coupling a controllerto a surface of an actuator; and means for sensing a characteristiccoupled to the means for coupling, wherein, when the means for couplingis coupled to the actuator, the means for sensing is adjacent thesurface to measure a characteristic of the means for coupling.
 20. Theapparatus of claim 19, wherein the means for coupling includes means forenabling a wire to extend between the means for sensing and thecontroller to operatively couple the means for sensing and thecontroller.